252 [Proc. B.N.F.C, 



A brief outline was next given of the order of succession of the 

 Cretaceous strata in those districts in England and France where 

 they are best developed. Their lithological and palaeontological 

 characteristics were described, and the very important fact of these 

 beds thinning out to the north and west of Europe was mentioned 

 as explanatory of the comparative thinness of this formation in 

 Ireland. Our Irish strata also illustrate this fact, for they are best 

 developed in the south and east of the County of Antrim, and 

 thin out to the west and north, in the counties of Londonderry and 

 Tyrone their thickness being very insignificant. 



The Irish Cretaceous rocks are seen in general cropping out 

 below the basaltic escarpment of the Miocene volcanic plateau of 

 the North-east of Ireland, and they invariably form a smaller 

 escarpment a little in advance of the igneous rocks, as they 

 resist denuding forces, whether sub-serial or marine, better than 

 the overlying volcanic rocks. On the Antrim side of the Lagan 

 valley, they may be seen stretching along the Belfast hills, like a 

 silver streak below the dark basaltic cliffs, and all around the 

 wave-washed shores of the County Antrim, as far to the northward 

 as the famous Giant's Causeway and Rathlin Island ; then turning 

 westwards, by the ruined towers of Dunluce Castle, to Ben Evenagh 

 mountain, overlooking Lough Foyle and the valley of the Roe, 

 along which they stretch southwards past Dungiven, and terminate 

 beyond Tamlaght and Stewartstown, in the County of Tyrone, 

 almost in the very heart of Ulster. 



Over this extended area of country, there is great variation in 

 the thickness and composition of the Cretaceous rocks. But it is 

 only in the south-eastern part of this district, particularly in the 

 vicinity of Belfast, where we find anything like completeness in 

 the succession of the beds. Along the elevated escarpment of the 

 Belfast range of hills, from Colin Glen— a few miles south-west of 

 Belfast— to Woodburn, on the north-east, we have good exposures ' 

 of these rocks in natural cliff sections, in quarries, and in the deep 



